Apparatus for coded signaling systems



7, 1956 P. M. BRANNEN I 2,758,201

APPARATUS FOR CODED SIGNALING SYSTEMS Filed Aug. 29, 1952 INVENTOR. Paui MT EPW712812.

BY wJm swb Hi5 HWWOHNE'Y.

APPARATUS non connn- SIGNALING SYSTEMS PaulM. Brannen, Verona, Pa., assignor to Westinghouse Air Brake Company, Wilmerding, Pa., a corporation ofiPennsylvania Application August 29, 1952, Serial No. 307,021 8 Claims. (Cl. 246-34) My invention relates to apparatus for coded signaling systems, and particularly to an improved code detecting and reverse code controlling arrangement for use in coded' signaling systems wherein reverse or feed-back coded energy is supplied to the system in addition to master or control coded energy.

In coded signaling systems, there are sometimes provided arrangements in which normal or master code energy is supplied at one end of a pair of conductors, such as the rails of a section of railway track, the energy being supplied in the form of spaced impulses of either direct or alternating current energy. This energy is supplied over the conductors or section rails to the other end'of the section, where the impulses operate amaster code following relay. During the intervals between the impulses of master code energy, impulses of feed-back or reverse code energy are supplied from the end of the current conductors or section rails at which the master code following relay is located, and such impulses are supplied over the conductors or rails to a reverse code following relay at the end of the sectionwhere the-master code' energy is supplied. The master code impulses which feed in one direction through the track sectionmay be employed to govern the operation of a signal which controls the movement of trafiic into the section at one end thereof, while the reverse code impulses may be used to govern the operation of a signal controlling the movements of traflic into the section from the opposite end.

The use of reverse code energy in a coded signaling system requires a means for governing the supply of the reverse code impulses in such manner that a short impulse of energy is supplied to the system each time that the master code following relay releases its contacts. Additionally, as in conventional coded signaling systems, means must be provided for detecting the recurrent or coded operation of the master code following track relay.

Accordingly, it is an object of my invention to provide an improved arrangement for detecting the operation of a code following relay and for governing the control of reverse code energy supplied to a pair of con ductors such as the rails of a section of railway track equipped with a coded signaling system.

Another object of my invention is to provide an improved code detecting and reverse code control circuit arrangement which requires the use of but one contact on the master code following relay.

Another object of my invention is to provide an improved code detecting and reverse code control circuit which utilizes the energy supplied to a storage capacitor for operating the reverse code control relay, and for additionally supplying energy to maintain the code detecting relay picked up, when the master code following track relay is recurrently operating its contacts.

Another object of my invention is to provide an improved coded detecting and reverse code control circuit arrangement, which utilizes the impulse of energy supplied to a storage capacitor when the master code follow- 2,758,201 patented Aug. 7, 1956 2. ing relay releases to momentarily pick up the contacts of a' reverse code control relay to thereby supply a pulse of reverse code energy to the current carrying conductors of the system from which the master code following relay receives energy, and to supply the energy which is thereby stored' in the capacitor to the winding of a slow release code detecting relay when the master code following relay is picked up, the apparatus being arranged so that only the energy which fiows during the time that the contact of the master code following relay is released is effectiveto pick up the reverse code control' relay.

Other objects of my invention and features of novelty thereof will be apparent from the following description taken in connection with the accompanying drawings.

In practicing my invention; I arrange the master code following relay, the reverse code control relay, the master code detecting relay, and a storage capacitor in such manner that each time that the contact of the master code following relay is released, energy is supplied through the winding of the reverse code control relay to the storage capacitor. This charging impulse is of relatively short duration, and accordingly, the contacts of the reverse code control relay are picked up momentarily while the charging current is flowing to the storage capacitor. When the value of thecharging current to the capacitor falls below the value necessary to keep the reverse code control relay contacts picked up, its contactswill release.- Thecontacts of the reverse code control relay govern a circuit by which the master code following relay is disconnectedfrom the circuit and the reverse code energy source is connected to the circuit. When the contacts of the master code following relay pick up on the next impulse of master code energy, the energy stored in the capacitor is supplied to the winding of a slow release code detecting" relay, which is proportioned and arranged so' that its contacts are sufficiently slow in releasing that they will not release during the periods between the impulses supplied to the winding of the relay by operation of the master code following relay. The apparatus is arranged so that only thecurrent which flows to the storage capacitor is effective to pick up the contacts of the reverse code relay. In one embodiment, this is accomplished by providing a reverse code control relay of the biased'type, having contacts which are'picked up when and only when energ flows in one" direction through the winding of the relay. In another embodiment of the invention, the reverse code control relay is of the conventional type buthas its winding connected in the circuit in such manner that only the charging energy to the'capacitor can flow therethrough, the'reverse code control'relay being disconnected from the circuit when the contact of the master code followingrelay is picked up.

I shall describe two forms of apparatus embodying my invention, andshall then point out the novel features thereof in claims.

In the drawings, Fig. l is a diagrammatic view of a stretch of railway track equipped with a-coded track circuit signaling system, and embodying a preferred form of my invention for governing the application of reverse code energy to the section rails.

Fig. 2 is a modification of the arrangement shown in Fig. 1, which differs therefrom in the use of a neutral reverse code control relay, rather than abiased reverse code control relay.

Referring to Fig. 1, there is shown a. stretch of railway track over which trains may move in. either direction as indicated by the double headed arrow. The rails 1 and 2of the stretch of railway. track are divided into the customary sections'byinsulated joints'3, the one section thereof being designated bythe reference character 1T.

Section IT is provided with wayside signals 18 at the left-hand end of the section and 28 at the right-hand end of the section to govern the entrance of traffic into section IT. For the control of signals 18 and 28, the section IT is provided with a coded track circuit, which employs master code energy for governing the operation of signal 18, this master code energy being supplied from the right-hand end of the section, and reverse code energy for the control of signal 25, this reverse code energy being supplied from the left-hand end of the section.

As shown, the signals 18 and 28 are of the well-known color light type, each having a green lamp G which when lighted indicates a clear section, and a red lamp R, which when lighted indicates an occupied section. The apparatus at the left-hand end of section 1T includes a master code following track relay lTR, a reverse code control relay RCR, of the biased type, in which the contacts of the relay are picked up when and only when current flows through the winding of the relay in the direction designated by the arrow, in this instance, from right to left. Additionally, there is provided a storage capacitor Q, and a code detecting relay til-IR, and a reverse code track battery RTB.

At the right-hand end of the section, there is provided a code transmitter CT, of the type well-known in railway signaling art, having one or more contacts which are recurrently operated at a predetermined rate, say, for example, 180 times per minute, as long as the operating winding of the code transmitter is connected to a suitable source of energy. The apparatus at the right-hand end of the section additionally includes a reverse code following track relay IRTR, a master code track battery 1TB, reverse code detecting relays FTP and BTP, which are arranged in the well-known FSA-BSA arrangement for detecting code following operation of the contacts of relay IRTR.

Energy for the operation of the apparatus other than the track relays is provided by suitable sources of low voltage direct current energy such as the batteries LB, shown at each location, the positive and negative terminals of which are designated by the reference characters l3 and N, respectively.

It is believed that the description of the apparatus embodying my invention will be enhanced by describing the operation of the equipment under various conditions. As shown, with the section 1T unoccupied, the code transmitter CT, which has its winding connected across the terminals B and N will operate its contact a recurrently at a predetermined rate, for example, 180 times per minute. Each time that the contact a of code transmitter CT picks up, the master code track battery 1TB is connected across the section rails 1 and 2 at the righthand end of the section. Accordingly, energy flows through a circuit which may be traced from the positive terminal of battery 1TB, over front contact a of the code transmitter CT, section rail 2 of the section 1T, through the winding of relay ITR, over back contact a of reverse code control relay RCR, section rail 1 of section 1T, and thence to the negative terminal of battery 1TB. As the result, the relay llTR will pick up its contact a. When the code transmitter CT releases its contact a, the supply of energy to the rails of section 1T from the battery lTB is cut oh, and accordingly the master code following track relay lTR will release its contact. When contact a of relay lTR is released, a circuit is provided for supplying energy to the capacitor Q, which includes back contact a of relay llTR, and the winding of the reverse code control relay RCR. It will be seen therefore that energy will be supplied from the low voltage direct current source through the winding of relay RCR to capacitor Q upon each release of contact a of relay HR. The charging current will flow at this time through winding of relay RCR from right to left, which is in the direction required to pick up the contact of relay RCR. Accord ingly, contact a of relay RCR will pick up momentarily during the charging impulse of the capacitor Q.

When contact a of relay RCR picks up, it interrupts the circuit for connecting the master code following track relay 1TR to the section rails and connects the reverse code energy battery RTB across the section rails at the left-hand end of section 1T.

When the charging current to the capacitor Q has decreased to an amount below that required to hold up the contact a of relay RCR, relay RCR will release its contact a, thereby disconnecting battery RTB from the section rails and again connecting the winding of relay lTR across the rails so that the following impulse of master code energy will be enabled to pick up the contact a of relay ITR. When contact a of relay ITR is picked up by the succeeding impulse of master code energy, the energy stored in the capacitor Q is discharged through the winding of the slow release code detecting relay IHR, by a circuit which includes the winding of the reverse code control relay RCR and front contact a of relay lTR. It will be seen that the direction of flow through the winding of relay RCR at this time is in such a direction as to prevent contact a of relay RCR from picking up.

Code detecting relay lHR is constructed and arranged so that its contacts will pick up and remain picked up when the impulses of energy are recurrently supplied to the winding of the relay from the capacitor Q by the circuit traced above. Accordingly, at this time the relay will be picked up and its front contact a establishes an obvious circuit for supplying energy to the green lamp G of signal 18, to thereby indicate that section IT is unoccupied.

At the right-hand end of the section, it will be seen that each time that contact a of the code transmitting device CT is released, the master code track battery 1TB is disconnected from the section rails and the winding of reverse code following relay IRTR is connected across the section rails. Accordingly, the relay lRTR will be operated by the impulses of reverse code energy which are fed from the left-hand end of the sections during the oil period of the master code. As a result of the recurrent operation of a contact a of relay lRTR, the code detecting relay FTP is picked up by a circuit including front contact a of relay IRTR, which circuit supplies energy to the winding of relay FTP. The relay FTP is of the slow release type and its contact a will remain picked up as long as impulses of energy are being recurrently supplied to the winding of the relay by the recurrent operation of contact a of relay IRTR. With contact a of relay FTP picked up, energy is supplied to the winding of relay BTP each time that contact a of relay lRT-R is released, by the circuit which includes back contact a of relay .lRTR and front contact a of relay FTP. Relay BTP is also slow in releasing, and it will remain picked up as long as impulses of energy are supplied to its winding by the recurrent operation of contact a of relay iRTR. The lighting circuit for signal 28 is governed by contact a of relay BTP, and accordingly, with the reverse code following relay IRTR in operation, contact a of relay BTP will be picked up and an obvious circuit is established for supplying energy to the green lamp G of signal 28.

From the foregoing, it will be seen that under normal conditions impulses of master code energy are supplied mm the right-hand end of section 1T to the apparatus at the left-hand end of the section, and, during the intervals between the impulses of master code energy, reverse code energy is supplied from the left-hand end of section H to the apparatus at the right-hand end of the section. The continuous supply of master code energy impulses and reverse code energy impulses result in the energization of relays lHR and BTP, with the result that the signals governed by these respective relays, namely signals 18 and 28, will display a green aspect, indicating that section IT is unoccupied.

it will nowbe assumed: thata. trainmoving. from. left to right passes signallS- and enters the section IT. The wheels and axles of the trainof section 11: willi shunt the supply of master code energy tothe relay ITR and, accordingly, its contact'awill release'andremain released. As a result, the supply of energyto the master. code detecting relay lHR is cut off, and'after a shorttime'interval, itscontact a will release. When contact a of relay lHR releases the supply ofenergy tothe. green lamp G of.

signal 18 is interrupted and a circuit is established for supplying energy to the redlamp R of. the signal, so that the signal displays a red aspect indicating an occupied section. Additionally, the-cessationof operation; of contact a of relay lTR willresult. in the relay RCRreleasing and remaining released; so thatenergy from the reverse code battery RT B is no longer supplied to the section. Moreover, the wheels and axles of the train in section 1T will shuntthesupply of reverse; code energy to the right-hand end'of. the section, so that relay lRTR is no longer supplied with energy upon the release of contact a of the code transmitter CT. Accordingly, contact a of relay lRTRwillsrelease.andremain released, and.

after a short intervalthe code detecting relays FTB and BTP will release in sequence, so that. contact a of relay BTP interrupts the supply. of energy to the green lamp G of signal 25 and establishes a circuit foe supplying energy to the red lamp R of signal 28,- with theresultthat signal 28 displays a red aspect: indicatingan occupiedsection,

When the train vacatessectioni T,.master code energy is again supplied to the rails of the section each time that contact a of code transmitter CT is picked up. Accordingly, the master code following track relay HR at the left-hand end-of the section will-again commence; to follow code, and the reverse code.- control relay-RCR will be operated as previously described to supply impulses of reverse code energy during-the intervals between the pulses of master. code energy, sothat: relay lRTR at the right-hand end of the sectionwill. be operated by the reverse code impulses. The reestablishment of the supply of coded energy tothe relays lTR and lRT-R- will cause their respective code detecting relays to become picked-up, with the result that the lighting circuit for the green lamp of signals 18 and 28 will again be established, indicating that section 1T is unoccupied.

In the case of a train moving from right to'let't'throughv the section, the wheels-and axles of the train will shunt the supply of master code energy at the right-hand end of the section, so that relay HR at the left endof the section will cease following code, and as a result the code detecting relay IHR will be released to thereby cause signal 18 to display its stop aspect. Also the reverse code following relay IRTR will no longer receive energy and as a result the code detecting relays FTP and BTP will be released so that signal 28 will display a stop aspect.

From the foregoing, it will be seen that the. arrangement embodying my invention as shown in Fig. 1! provides a simple and effective means for supplying. reverse code control energy to a pair of current carrying conductors such as the rails of a section of railway track, and additionally, provides-for the detection of operation of the master code following relay. The" arrangement is ad vantageous from the standpoint that only a single contact is required on the master codefollowing track relay, which means that this relay maybeconstructed and arranged so as to be quite. sensitive, thereby lengthening the distance over which it'may be operated. This is particularly advantageous in a coded railway track circuit, since longer track circuits may be operated and fewer cut sections are required for each stretch of track between signals.

Referring now to Fig. 2 of. the drawings, there is shown a modification of the arrangement of apparatus in Fig. l, which utilizes a neutral relay for the reverse code control relay, rather than a biased relay such as shown in Fig. l. In the arrangement shown in Fig. 2,

the charging circuit for the capacitor Q includes the. winding of the relayRCR, in addition to the back contacta of the-master code-following relay lTR. It will be apparent that the charging current for the capacitor wil'l'flow through the winding: of the relay RCR so that itwill momentarily pick up its contacts for the durationof time in which the charging current exceeds the current required to-pick up and hold up the relay contact; The. dischargingcircuit for the capacitor Q includes only thefrontcontact a of relay l-TR, so that when relay 117R is picked up the energy storedin capacitor Qis discharged. directly. through the winding of the code detecting relay I I-IR. without having to pass through the winding of the: relay RCR. The operation of the arrangement shown: in Fig. 2.is similar to that-described previously in connection with. Fig. 1, and a. detailed, description. of" this secondarrangement isdeemedunnecessary.

Although I have herein shown andidescribed. only two forms of apparatus for coded signaling. systems, itswill be apparent to those skilled in the art that various changes and modifications may be made thereinw-ithin the scopeof the appended'claims without departing from the spiritand scopev of my invention.

Having thus described my invention, what claim is:

l. Incombination, atpair of current carrying conductors, means connected to one end'of said conductors for recurrently. supplying spaced impulsesof electrical energy thereto and for connecting relay means tosaid conductors duringthe intervals between. said spaced impulses, and' means connected to the otherv end of said conductors for detecting the recurrent supply thereto of said spaced impulses andfor supplying; pulses-of electrical energy to said conductors during. the=intervals between saidspaced pulses, said-last-namedimeanscomprising a master code following relay having a contact which is operated from a first' to a, second: position each time that an impulse of energy issupplied to awinding ofthe-relay, a reverse codev control relay having a contact which is picked up or released according as energy is or is not supplied to a winding of the relay, 2; slow release code detecting relay having contacts which are pickedup or released according asimpulses of energy are or are not supplied to the winding of the relay, a first source of electrical energy, an energy storage device for storing energy supplied thereto from saidfirst source, a first circuit for supplying energy from said first source to said energy storage device including said contactof said master code following relay closed inits firstzposition and the winding of said reverse code control relay, a second circuit for supplying energy from said energy storage device to the winding of said code detecting relay including said contact of said master code following relay closed in its secondposition', a. second source of electrical energy, circuit means governed by said contact of said reverse code control relay for selectively. connecting said second source of energy and the winding of said master code following relay to said conductors according asthe contact of said reverse code control relay is picked up or released, and circuit means governed by the contacts of said code detecting relay.

2. In combination, a pair of current'carryingconductors, means connected to one end of said conductors for recurrently supplying spaced impulses ofelectrical energy thereto and for, connectingrelay meansto said conductors during the intervals between said spaced impulses, and means connected to the other endof said conductors for detecting the recurrent supply thereto of said spaced impulses and for supplying pulses of electrical energy to said conductors during the intervals between said spaced pulses,

said last named means comprising a master code following relay having a contact which is operated from a first to a secondposition each time that animpulse of energy issuppliedit'o awinding ofthe relay, a'reverse code control relay having a contact which is picked up or released according as energy is or is not supplied to a winding of the relay, a slow release code detecting relay having contacts which are picked up or released according as impulses of energy are or are not supplied to the winding of the relay, a first source of electrical energy, a capacitor for storing energy supplied thereto from said first source, a first circuit for supplying energy from said first souce to said capacitor including said contact of said master code following relay closed in its first position and the winding of said reverse code control relay, a second circuit for supplying energy from said capacitor to the winding of said code detecting relay including said contact of said master code following relay closed in its second position, a second source of electrical energy, circuit means governed by said contact of said reverse code control relay for selectively connecting said second source of energy and the winding of said master code following relay to said conductors according as the contact of said reverse code control relay is picked up or released, and circuit means governed by the contacts of said code detecting relay.

3. In combination, a pair of current carrying conductors, means connected to one end of said conductors for recurrently supplying spaced impulses of electrical energy thereto and for connecting relay means to said conductors during the intervals between said spaced impulses, and means connected to the other end of said conductors for detecting the recurrent supply thereto of said spaced impulses and for supplying pulses of electrical energy to said conductors during the intervals between said spaced pulses, said last named means comprising a master code following relay having a contact which is operated from a first to a second position each time that an impulse of energy is supplied to a winding of the relay, a reverse code control relay having a contact which is picked up or released according as current does or does not fiow through a winding of the relay in a given direction, a slow release code detecting relay having contacts which are picked up or released according as impulses of energy are or are not supplied to a winding of the relay, a first source of electrical energy, an energy storage device for storing energy supplied thereto from said first source, a first circuit for supplying energy from said first source to said energy storage device including said contact of said master code following relay closed in its first position and the winding of said reverse code control relay, the parts being arranged so that the current which fiows through the winding of said reverse code control relay at this time is in the direction effective to pick up the contact of said reverse code control relay, a second circuit for supplying energy from said energy storage device to the winding of said code detecting relay including the contact of said master code following relay closed in its second position and the winding of said reverse code control relay, the current flow through the winding of the reverse code control relay being in the direction which is ineffective to pick up the contacts of the reverse code control relay, a second source of electrical energy, circuit means governed by said contact of said reverse code control relay for selectively connecting said second source of energy and the winding of said master code following relay to said conductors according as the contact of said reverse code control relay is picked up or released, and circuit means governed by the contacts of said code detecting relay.

4. In combination, a pair of current carrying conductors, means connected to one end of said conductors for recurrently supplying spaced impulses of electrical energy thereto, and for connecting relay means to said conductors during the intervals between said spaced impulses, and means connected to the other end of said conductors for detecting the recurrent supply thereto of said spaced impulses and for supplying pulses of electrical energy to said conductors during the intervals between said spaced pulses, said last named means comprising a master code following relay having a contact which is operated from a first to a second position each time that an impulse of energy is supplied to a winding of the relay, a reverse code control relay having a contact which is picked up or released according as current does or does not flow through a winding of the relay in a given direction, a slow release code detecting relay having contacts which are picked up or released according as impulses of energy are or are not supplied to a winding of the relay, a first source of electrical energy, a capacitor for storing energy supplied thereto from said first source, a first circuit for supplying energy from said first source to said capacitor including said contact of said master code following relay closed in its first position and the winding of said reverse code control relay, the parts being arranged so that the current which flows through the winding of said reverse code control relay at this time is in the direction effective to pick up the contact of said reverse code control relay, a second circuit for supplying energy from said capacitor to the winding of said code detecting relay including the contact of said master code following relay closed in its second position and the winding of said reverse code control relay, the current flow through the winding of the reverse code control relay being in the direction which is ineffective to pick up the contacts of the reverse code control relay, a second source of electrical energy, circuit means governed by said contact of said reverse code control relay for selectively connecting said second source of energ and the winding of said master code following relay to said conductors according as the contact of said reverse code control relay is picked up or released, and circuit means governed by the contacts of said code detecting relay.

5. In combination, a pair of current carrying conductors, means connected at one end of said conductors for recurrently supplying spaced impulses of electrical energy thereto and for connecting relay means to said conductors during the intervals between said spaced impulses, and means connected to the other end of said conductors for detecting the recurrent supply thereto of said spaced impulses and for supplying pulses of electrical energy to said conductors during the interval between said spaced pulses, said last-named means comprising a master code following relay having a contact which is operated from a first to a second position each time that an impulse of energy is supplied to a winding of the relay, a reverse code control relay having a contact which is picked up or released according as energy is or is not supplied to a winding of the relay, a slow release code detecting relay having contacts which are picked up or released according as impulses of energy are or are not supplied to a winding of the relay, a first source of electrical energy, an energy storage device for storing energy supplied thereto from said first source, a first circuit for supplying energy from said first source to said energy storage device including said contact of said master code following relay closed in its first position and the winding of said reverse code control relay, the winding of said reverse code control relay being interposed in said first circuit between said contact of the master code following relay and said first source, a second circuit for supplying energy from said energy storage device to the winding of said code detecting relay including said contact of said master code following relay closed in its second position, a second source of electrical energy, circuit means governed by said contact of said reverse code control relay for selectively connecting said second source of energy and the winding of said master code following relay to said conductors according as the contact of said reverse code control relay is picked up or released, and circuit means governed by the contacts of said code detecting relay.

6. in combination, a pair of current carrying conductors, means connected at one end of said conductors for recurrently supplying spaced impulses of electrical energy thereto and for conn.;cting relay means to said conductors during the intervals between said spaced impulses, and means connected to the other end of said conductors for detecting the recurrent supply thereto of said spaced impulses and for supplying pulses of electrical energy to said conductors during the interval between said spaced pulses, said last named means comprising a master code following relay having a contact which is operated from a first to a second position each time that an impulse of energy is supplied to a winding of the relay, a reverse code control relay having a contact which is picked up or released according as energy is or is not supplied to a winding of the relay, a slow release code detecting relay having contacts which are picked up or released according as impulses of energy are or are not supplied to a winding of the relay, a first source of electrical energy, a capacitor for storing energy supplied thereto from said first source, a first circuit for supplying energy from said first source to said capacitor including said contact of said master code following relay closed in its first position and the winding of said reverse code control relay, the winding of said reverse code control relay being interposed in said first circuit between said contact of the master code following relay and said first source, a second circuit for supplying energy from said capacitor to the winding of said code detecting relay including said contact of said master code following relay closed in its second position, a second source of electrical energy, circuit means governed by said contact of said reverse code control relay for selectively connecting said second source of energy and the winding of said master code following relay to said conductors according as the contact of said reverse code control relay is picked up or released, and circuit means governed by the contacts of said code detecting relay.

7. In combination with a section of railway track, means connected to one end of said section for recurrently supplying spaced impulses of electrical energy to the section rails and for connecting the winding of a re verse code following track relay to the section rails during the intervals between said spaced impulses, a master code following track relay, a reverse code energy source, and a reverse code control relay, located at the other end of said section, circuit means including a contact of said reverse code control relay for connecting the winding of said master code following track relay across the rails of said section when said reverse code control relay is released and for connecting said source of reverse code energy across the section when said reverse code control relay is picked up, a slow release code detecting relay for detecting the recurrent operation of said master code following track relay, and means for governing said reverse code control relay and said code detecting relay comprising a source of electrical energy, a storage device for storing electrical energy supplied thereto from said source, a first circuit including the winding of said reverse code control relay and a back contact of said master code following track relay for supplying energy from said source to said energy storage device, and a second circuit including a front contact of said master code following relay for supplying energy from said storage device to the winding of said code detecting relay.

8. In combination with a section of railway track, means connected to one end of said section for recurrently supplying spaced impulses of electrical energy to the section rails and for connecting the winding of a reverse code following track relay to the section rails during the intervals between said spaced impulses, a master code following track relay, a reverse code energy source, and a reverse code control relay, located at the other end of said section, circuit means including a contact of said reverse code control relay for connecting the winding of said master code following track relay across the rails of said section when said reverse code control relay is released and for connecting said source of reverse code energy across the section when said reverse code control relay is picked up, a slow release code detecting relay for detecting the recurrent operation of said master code following track relay, and means for governing said reverse code control relay and said code detecting relay comprising a source of electrical energy, a capacitor for storing electrical energy supplied thereto from said source, a first circuit including the winding of said reverse code control relay and a back contact of said master code following track relay for supplying energy from said source to said capacitor and a second circuit including a front contact of said master code following relay for supplying energy from a capacitor to the winding of said code detecting relay.

References Cited in the file of this patent UNITED STATES PATENTS 2,309,174 Dodd Jan. 26, 1943 2,355,334 Scheg Aug. 8, 1944 2,479,684 Hufnagel Aug. 23, 1949 2,559,391 Blosser et al. July 3, 1951 2,606,234 Nijman Aug. 5, 1952 2,607,001 Jerome Aug. 12, 1952 2,659,880 Dodd Nov. 17, 1953 FOREIGN PATENTS 448,549 Great Britain June 10, 1936 481,054 Great Britain Mar. 4, 1938 

